Condoms have long been useful for contraceptive purposes, and are of ever increasing importance as a widely accepted and easily administered means of preventing the transmission of disease. In view of the widespread reliance on condoms, stringent requirements for leakage avoidance have been established. Leak testing has thus become a critical step in condom manufacture.
In current practice, condoms are leak tested by electronic means. According to these tests, a condom is placed over an electrically conductive rod (or "mandrel") which conforms in shape to the condom but is approximately 12% to 17% larger in diameter. The mandrel thus causes the condom to expand, enlarging any pinholes present in the condom to facilitate detection.
Leak detection is then conducted according to one of two methods. One method is a "wet test" method, in which the mandrel with condom stretched over it is immersed in a bath of electrically conductive aqueous solution. Approximately one volt of electrical potential is imposed between the solution and the stainless steel mandrel, and the system is monitored to detect any electrical current which results. The passage of a current indicates that a pinhole is present in the condom, and the condom is rejected.
The second method is a "dry test" method, in which the outer surface of the condom stretched over the mandrel is placed in contact with rotating conductive brushes or a fine stainless steel screen. An electrical potential of approximately 1000 volts is imposed between the mandrel and the brushes or screen, and the system is monitored to detect any electrical current arcing between the mandrel and the brushes or screen. If current is detected, the condom is either too thin or contained a hole before placement on the mandrel, and is rejected.
The wet and dry electronic test methods were designed for latex condoms, and both have limitations when applied to condoms of materials other than latex. In the wet test, the condom may become hydrated, causing its electrical conductivity to rise and yield a false test result. As a result, the wet test is not suitable for many alternative materials, including polyurethane.
In the dry test, the usual practice is to employ a testing mandrel that is significantly larger than the condom. Stretching the condom over such a mandrel increases the size of any pinholes that may be present, thereby increasing the sensitivity of the test. In addition, a condom stretched over an over-sized mandrel can only be removed from the mandrel by rolling the bead downwards. While this generally produces a rolled condom ready for lubrication and packaging, with certain materials a condom removed in this manner is too tightly rolled for subsequent use. Furthermore, the high voltage used in the dry electronic test may lead to dielectric breakdown of materials other than latex, particularly in the case of very thin condoms.
Finally, condoms made of materials other than latex may need to be shaped differently from latex condoms. These shapes may make it impractical to load such condoms onto electronic test mandrels, particularly when the mandrels are oversized.